Masanori Maruoka

Study on Properties of Mortar and Concrete Using Belite-Gehlenite Clinker as Fine Aggregate

In recent years, there has been a strong demand for sustainable concrete structures. In addition, the cement production has been a downward trend in Japan. However, the amount of wastes and by-products used for cement production has been increased. Therefore, it’s necessary to explore new utilization of a cement clinker besides the cement. The Gehlenite clinker is produced from large amounts of recycled industrial waste, such as construction waste soil, sewage sludge, waste clay and coal ash. This study investigated the effect of using Gehlenite clinker as fine aggregate on various properties of mortar and concrete. The results show that, compared to mortar containing a conventional fine aggregate, mortar containing clinker aggregate has higher compressive strength, less drying shrinkage, and lower carbonation rate. In addition, mortar was evaluated by self-healing performance. Moreover, the properties of concrete are almost the same as mortar in compressive strength and drying shrinkage. In this paper, in order to investigate the mechanism of carbonation of mortar Gehlenite clinker was used as fine aggregate. The results show that, when the fine aggregate is replaced with Gehlenite clinker, the representative porosity in the transition zone is reduced by approximately half and this improves resistance to carbonation.

Development of spraying agent for reducing drying shrinkage of mortar

Mortar used to repair is sometimes exposed to drying state in early ages after construction and a few days later water is sprayed frequently on the surface of the mortar in order to prevent cracks. This research studied on shrinkage characteristic of mortar subjected to drying conditions like this. The result showed that the water spraying on the mortar after initial drying did not have any effect to prevent shrinkage, but increased. And it also showed when various chemical agents are mixed and used in watersprayingit had the prevention effect on shrinkage. This report was to understand this kind of phenomenon and clarify the mechanism. In addition, based on the results, the new spraying agent was developed to reduce drying shrinkage.

FUNDAMENTAL STUDY ON PROPERTIES OF ULTRA-HIGH-STRENGTH FIBER-REINFORCED CONCRETE CURED AT AMBIENT-TEMPERATURE

This research investigates candidate materials for ultra-high strength fiber reinforced concrete（UFC）that can achieve high bending strength over than 45N/mm² by using ordinary Portland cement（OPC）and curing at ambient temperature. In this research, prototype high-alite cement（HAC）is also used for comparison. As testing results, the target workability was obtained at lower dosage of super plasticizer in the condition of using OPC as base material. Then, as the content of blast-furnace slag powder（Blane value of 8,000cm²/g grade）increases, the mortar flow value increases greatly. And mortar flow value increases greatly as the specific surface area of fine blast-furnace slag powder increases. In these tests, HAC was used for developing enough strength at early age. The compressive strength at the age of 1 day, that of UFC using HAC was higher than that of UFC using OPC, but at the age of 28 days, UFC using OPC showed higher compressive over than 170N/mm² and bending strength over than 45N/mm², and it is higher than that of UFC using HAC.本研究では混和材の反応性を高めることを目的として試作した高エーライトセメントと普通ポルトランドセメントを用い常温硬化型鋼繊維補強コンクリートの製造可能性を検討するとともに、その基本性状を把握することを目的として実験を行った。その結果、普通ポルトランドセメントを用いた場合の方が高性能AE減水剤の添加率が抑えられ、フレッシュ性状に優れることが確認できた。普通ポルトランドセメントをベースセメントとして用いた場合、高炉スラグ微粉末の混和率および比表面積の増加に伴い、流動性は向上する結果となった。また、強度試験においては高エーライトセメント適用に伴う初期強度効果が得る。材齢28日においては圧縮強度170N/mm2、曲げ強度45N/mm2となり強度発現性に関しても普通ポルトランドセメントを用いた方が優れることが確認できた。

Development of Cross Section Repairing Material with High Thixotropy

The performance features required from cross section repairing materials include excellent bonding, workability, and the ability to be applied in thick coatings without cracking. At present polymer materials are normally used as cross section repairing materials. The problems with these materials include high viscosity and as such both workability and durability are poor. Therefore, in this research, a high thixotropy material was developed without using polymer, and its performance was evaluated. This material has good workability due to its high thixotropy. In spray tests it was possible to spray a wall surface to about 140 – 150 mm thickness, and a ceiling surface to about 60 mm thickness. Moreover, it has high bond strength and high compressive strength, and low drying shrinkage.

STUDY ON RELATIONSHIP BETWEEN PROPERTIES OF LIMESTONE POWDER AND FRESH PROPERTIES OF MORTAL

石灰石微粉末の銘柄, 製造工程の違いを把握し, 化学的, および鉱物的, 物理的特性が, 石灰石微粉末を混和したモルタルおよびコンクリートのレオロジー特性に及ぼす影響について検討した結果, 以下のことが明らかになった.石灰石微粉末を混和したモルタルの流動性は石灰石微粉末のCaOの純度, 原石に含まれる不純物, 製造過程で混入するダスト, 粉末度, セメントの一部を置き換える場合の置換率などの影響を受ける. これらは, 粉体の拘束水量, 高性能AE減水剤吸着量を変化させるためと考えられる. また, 原石の結晶の大きさもわずかながら影響し, 結晶の小さい原石を粉砕して製造した石灰石微粉末を混和したモルタルは流動性生が向上した.